【作者】 王彦芳；

【导师】 董闯；

【作者基本信息】 大连理工大学 ， 材料科学与工程， 2006， 博士

【摘要】 近年来发现了一系列具有较大玻璃形成能力的合金体系,如Zr基、Ti基、Mg基、Cu基等,并用铸造的方法获得毫米至分米量级的块体非晶合金。块体非晶合金与许多金属间化合物的主要组元之间都有较大的负混合焓,满足发生燃烧合成反应的热力学条件,因而可以通过自蔓延反应合成。本文从块体非晶合金的内在热力学属性出发,系统研究了强放热反应体系、弱放热反应体系和添加组元的多组元体系的激光诱导燃烧合成行为和合成产物的组织结构特征,初步建立了激光诱导燃烧合成非晶合金的基本框架。 首先,以电子浓度和原子尺寸判据设计了Zr-Al-Ni、Zr-Al-Ni-Ti和Zr-Al-Ni-Cu合金。XRD和热分析发现,在Zr-Al-Ni体系中,加入少量的Ti,可以形成块体非晶合金,但是其热稳定性降低,玻璃形成能力变化不大,基本保持稳定;添加Cu元素使Zr-Al-Ni非晶合金的稳定性下降,但玻璃形成能力提高。 Zr-Al-Ni是典型的块体非晶合金形成体系,Zr-Al-Ni体系的混合焓约为-50kJ/mol,为典型的强放热反应体系。本文以此合金为例,研究强放热体系激光诱导燃烧合成产物的组织结构特征。合成产物主要由Zr₂Ni,Zr₆Al₂Ni和Zr₅AlNi₄相组成,没有非晶相存在,这与材料体系的强放热特性有关。研究Zr-Al-Ni燃烧合成机理发现,在620℃发生了Zr-Al之间的放热反应,形成了ZrAl金属间化合物;1080℃发生了Zr-Ni之间的放热反应,形成了Zr₂Ni相。 添加第三组元以降低反应热是控制燃烧合成过程的有效途径。在Zr-Al-Ni强放热反应体系中添加Ti和Cu元素后混合焓降到了-45～-30 kJ/mol,均获得了含非晶相的合成产物。Zr-Al-Ni-Ti产物主要由非晶、面心立方的Zr₂Ni相、Zr₆Al₂Ni六角相和α-Ti/Zr固熔体组成,其中Zr₅₅Ti_10.8Al_17.1Ni_17.1成分的非晶体积含量约为一半;Zr-Al-Ni-Cu合成产物主要由非晶、Zr₂Ni、Zr₂Al和Zr₂Cu相组成,其中Zr_54.4Al₂₀Ni_17.2Cu_8.4和Zr₅₅Al₁₈Ni_13.5Cu_13.5成分的非晶含量达到一半左右。 Cu-Zr-Al合金体系的混合焓约为-23kJ/mol,为相对弱放热的反应体系。本文以此合金体系为例,研究了弱放热反应体系的激光诱导燃烧合成行为和合成产物的组织结构特征。产物主要由非晶、α-Zr,Zr₂Cu,Cu₁₀Zr₇和Cu₈Zr₃相组成,非晶、纳米晶含量大约在20%～60%。其中Cu_59.6Zr_36.9Al_3.5合金的非晶、纳米晶含量超过一半。透射电镜和XRD更多还原

【Abstract】 Bulk metallic glasses （BMGs） with high thermal stability and large glass-forming ability （GFA） have been found in Zr-based, Ti-based, Mg-based and Cu-based alloys. They can be fabricated by various slow cooling solidification methods such as copper mold casting and water quenching. Bulk metallic glasses, like many crystalline intermetallics, have large negative enthalpy of mixing among their major constituent elements, and hence are potential candidates for combustion synthesis. Based on this characteristic, we developed a laser-induced combustion synthesis （LCS） technique to fabricate amorphous-containing alloys. In this thesis, LCS of strong-exothermic reaction system, weak-exothermic reaction system and multi-element system are systematically studied. A basic frame of the LCS of amorphous-containing alloys is established.First, a series of Zr-Al-NK Zr-Al-Ni-Ti and Zr-Al-Ni-Cu alloys are designed according to the electron concentration and average atomic size criteria. The XRD and thermal analysis results show that pure amorphous state is reached only within a small Ti addition in Zr-Al-Ni. Adding a small amount of Ti deteriorates the thermal ability, but maintains the same glass forming ability. Adding Cu decreases the thermal stability, but increases the glass forming ability.The Zr-Al-Ni ternary system is a typical glass-forming system satisfying the combustion synthesis requirement. The mixing enthalpy of Zr-Al-Ni ternary system is about -50 kJ/mol. As a typical case of strong-exothermic reaction system, the LCS products are studied in this paper. The XRD results show that the products mainly consist of Zr₂Ni, Zr₆Al₂Ni and Zr₅AlNi₄ phases, but no amorphous phase is detected, which is probably associated with the strong-exothermic reaction system and the characteristic of LCS. The Zr-Al exothermic reaction occurres at 620℃ to form ZrAl. At 1080℃, a Zr-Ni exothermic reaction occurres to form Zr₂Ni.Adding third elements as diluting agents is a useful means to control the combustion synthesis process. Amorphous-containing products are obtained by adding Ti or Cu into the Zr-Al-Ni system. The LCS Zr₅₅Ti_10.8Al_17.1Ni_17.1 product contains about 50% amorphous phase besides the face-centered cubic Zr₂Ni-type phase, the a-Ti/Zr solid solution, and the hexagonal Zr₆Al₂Ni phase. The LCS Zr-Al-Ni-Cu products mainly consist of amorphous, Zr₂Ni, Zr₂Al andintermetallics, and about half amorphous contains are observed in Zr54.4Al20Nin.2Cu8.4 andExtensive attention has been paid to the Cu-based BMGs due to their high glass forming ability in combination with good mechanical properties as well as relative low material cost. The mixing enthalpy of Cu-Zr-Al ternary system is about -23 kJ/mol. As a typical case of weak-exothermic reaction system, the LCS products are studied. The LCS products mainly consist of amorphous, a-Zr, Zr2Cu, CuioZr7 and CuaZr3, The amorphous and nono-crystalline phases content over 50% in volume is obtained for the CusaeZrafi.pAb.s alloy as estimated from the area of the broad peak in the XRD spectrum. Crystalline phases tl-Z^Cu, oc-Zr and oC-CuioZr? phases are identified both by TEM and XRD. TEM and HRTEM results show that the microstructure is characterized by inhomogeneously distributed amorphous, nano Z^Cu, relatively gross （-lOOnm） Z^Cu, and large grain CuioZr?.Based on the systematic study of the above three typical powder materials systems, a basic frame of LCS of amorphous-containing alloys is established. Adding diluting agents is a useful way to control the combustion synthesis process. High amorphous content is easily obtained in weak-exothermic reaction systems with high glass-forming ability than in strong-exothermic reaction systems. Tg/Tl>0.5 and AH >-40 kJ/mol is required for obtaining high amorphous contents.更多还原